P - (Pressure) - omni directional - moving coil only.
R - (Ribbon) - bi-directional (figure of 8) - ribbon only.
C - (Cardioid) - uni-directional - combining both elements.
The 4033A was somewhat of a compromise as it tended to be "toppy" in all three positions. Nevertheless, it was the standard TV Boom microphone for many years and was also used on Radio OBs where its cardioid response was useful for rejecting colouration from PA.